code: def register_dwi_to_template(
      dwi,
      gtab,
      dwi_affine=None,
      template=None,
      template_affine=None,
      reg_method="syn",
      **reg_kwargs,
  ):
      """Register DWI data to a template through the B0 volumes.
  
      Parameters
      ----------
      dwi : 4D array, nifti image or str
          Containing the DWI data, or full path to a nifti file with DWI.
      gtab : GradientTable or sequence of strings
          The gradients associated with the DWI data, or a sequence with
          (fbval, fbvec), full paths to bvals and bvecs files.
      dwi_affine : 4x4 array, optional
          An affine transformation associated with the DWI. Required if data
          is provided as an array. If provided together with nifti/path,
          will over-ride the affine that is in the nifti.
      template : 3D array, nifti image or str
          Containing the data for the template, or full path to a nifti file
          with the template data.
      template_affine : 4x4 array, optional
          An affine transformation associated with the template. Required if data
          is provided as an array. If provided together with nifti/path,
          will over-ride the affine that is in the nifti.
  
      reg_method : str,
          One of "syn" or "aff", which designates which registration method is
          used. Either syn, which uses the :func:`syn_registration` function
          or :func:`affine_registration` function. Default: "syn".
      reg_kwargs : key-word arguments for :func:`syn_registration` or
          :func:`affine_registration`
  
      Returns
      -------
      warped_b0, mapping: The fist is an array with the b0 volume warped to the
      template. If reg_method is "syn", the second is a DiffeomorphicMap class
      instance that can be used to transform between the two spaces. Otherwise,
      if reg_method is "aff", this is a 4x4 matrix encoding the affine transform.
  
      Notes
      -----
      This function assumes that the DWI data is already internally registered.
      See :func:`register_dwi_series`.
  
      """
      dwi_data, dwi_affine = read_img_arr_or_path(
          dwi, affine=dwi_affine
      )
  
      if template is None:
          template = dpd.read_mni_template()
  
      template_data, template_affine = read_img_arr_or_path(
          template, affine=template_affine
      )
  
      if not isinstance(gtab, dpg.GradientTable):
          gtab = dpg.gradient_table(*gtab)
  
      mean_b0 = np.mean(dwi_data[..., gtab.b0s_mask], -1)
      if reg_method.lower() == "syn":
          warped_b0, mapping = syn_registration(
              mean_b0,
              template_data,
              moving_affine=dwi_affine,
              static_affine=template_affine,
              **reg_kwargs,
          )
      elif reg_method.lower() == "aff":
          warped_b0, mapping = affine_registration(
              mean_b0,
              template_data,
              moving_affine=dwi_affine,
              static_affine=template_affine,
              **reg_kwargs,
          )
      else:
          raise ValueError(
              "reg_method should be one of 'aff' or 'syn', but you"
              " provided %s" % reg_method
          )
  
      return warped_b0, mapping
  
imports: from warnings import warn
  import re
  import collections.abc
  from functools import partial
  import numbers
  import numpy
  import nibabel
  from dipy.align.metrics import CCMetric, EMMetric, SSDMetric
  from dipy.align.imwarp import SymmetricDiffeomorphicRegistration, DiffeomorphicMap
  from dipy.align.imaffine import transform_centers_of_mass, AffineMap, MutualInformationMetric, AffineRegistration
  from dipy.align.transforms import TranslationTransform3D, RigidTransform3D, RigidScalingTransform3D, RigidIsoScalingTransform3D, AffineTransform3D
  import dipy.core.gradients
  import dipy.data
  from dipy.align.streamlinear import StreamlineLinearRegistration
  from dipy.tracking.streamline import set_number_of_points
  from dipy.tracking.utils import transform_tracking_output
  from dipy.io.streamline import load_trk
  from dipy.io.utils import read_img_arr_or_path
  from dipy.io.image import load_nifti, save_nifti
label_desc: Use image node_id 3 for calling a global function with example usage: register_dwi_to_template(dwi, gtab, dwi_affine, template, template_affine, reg_method) and returns: warped_b0,  mapping